This invention relates generally to system peripherals and, more particularly, to managing cables for system peripherals to prevent entanglement and to conveniently adjust the slack of the cables.
A variety of system peripherals are widely used to provide interface with a system host such as a personal computer. Among the most common input peripherals include computer mouse devices, keyboards, and joysticks, while printers, monitors, and speakers are examples of output peripherals. Conventional interfaces between the system host and system peripherals such as PS/2 interface and parallel ports can be cumbersome and difficult to use. Conventional interfaces also place severe restrictions on the number of peripherals that can be connected to the system host.
A more robust interface standard known as the Universal Serial Bus (USB) has been developed for providing interface among devices such as the integration of many peripherals to a system host. For example, the USB in a personal computer system connects computer peripherals to a personal computer through a single connector type using a tiered-star topology. A host controller of the USB interfaces with the host processor inside the personal computer. The host controller controls all accesses to USB resources and monitors the bus's topology. The USB has a "hot-swapping" feature that allows the user to attach or remove a peripheral without the need to shut down and restart the system host.
A USB hub provides USB attachment points for USB devices, as shown in FIG. 1. The USB hub includes a hub controller coupled to a hub repeater which is coupled to an upstream port or root port (port 0) for connection to a system host. The hub repeater is coupled to N number of downstream ports providing connection for N number of downstream USB-compatible devices. The USB hub is responsible for transferring data both upstream and downstream. All data transfers occur between the host computer and the peripheral devices.
The host controller includes a root hub, but a USB system may include other hubs that provide easy plug-in points for peripheral devices. This permits the user to "daisychain" multiple devices together to form a system interface tree, as illustrated in FIG. 2. The host is at the root of the system interface tree, while the peripheral devices are located on branches of the tree. A system interface such as a USB hub resides at each intersection. In the embodiment shown, the hubs are conveniently built into the peripheral devices. Each system interface hub has one or more downstream ports providing connection for one or more downstream peripherals. When the host transfers data to a device, data is transferred downstream through all hubs, from an upstream port to all non-disabled downstream ports to all other hubs and devices. On the other hand, when data is transferred from a device to the host, the transfer occurs upstream only on the direct path to the host. The USB also distributes electrical power to the peripherals by letting the system host sense automatically the power that is required and deliver it to low-power peripheral devices. External power supplies are needed only for high power peripheral devices.